Incorporation of carbohydrates into abnormal thyroglobulin in an experimental rat thyroid tumor.

Abstract

Previous findings indicated that in line 1–1C2 of experimental rat thyroid tumor there is decreased secretion of 19S thyroglobulin associated with a lack of incorporation of sialic acid into thyroglobulin and sialyltransferase activity in the tumor. In the present work we studied another tumor line, 1–8, in which particle bound iodopro-tein is also increased. This tumor, however, secretes an abnormal form of thyroglobulin. Soluble and digitonin-solubilized iodoproteins were examined in tumor labeled in vitro with N-acetylmannosamine, galactose, mannose, N-acetyl-glucosamine, leucine and iodine. About half of each label except galactose and N-acetyl-mannosamine was in the pellet after digitonin extraction and the remainder was evenly distrib-uted between soluble and solubilized fractions. After galactose labeling, the soluble fraction con-tained relatively more labeled protein; after N-acetylmannosamine, the pellet content was higher but most of the remainder was in the soluble fraction. The soluble and so...